Doing calculations with bc on one field Post: 302586335

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Top Forums UNIX for Dummies Questions & Answers Doing calculations with bc on one field Post 302586335 by edehont on Sunday 1st of January 2012 01:19:11 AM

01-01-2012

Registered User

If you want (slash need) to stick to sed and bc, try this:

Code:

sed 's/^\(.*:\)\([0-9]*\),*\([0-9]*\):\([0-9]*\),\([0-9]*\)/print \"\1\2,\3:\4,\5:\",\4\.\5-\2\.\3,\"\n\"/' beurs.txt|bc|sed 's/\(\.\([0-9]*\)\)$/,\2/'

Explanation: Don't abuse a cat! First turn the line into a string by enclosing it in '"'. Add a comma, the expression, a comma and a newline. Feed this to the print function of bc.

Finally translate the last '.' into a ',', because bc is not aware of locale-issues. In the Netherlands we use a decimal ',' instead of a '.'.

When nesting groups in sed, the deeper nested groups get higher numbers. e.g.: (a(b(c))) \1=abc, \2=bc, \3=c. This way we can get rid of the '.'. Of course this applies not only to sed but to other regular expression environments as well.

I've tested this on Ubuntu 11.10.

Quote:

bash --version
GNU bash, versie 4.2.10(1)-release (x86_64-pc-linux-gnu)
sed --version
GNU sed versie 4.2.1
bc --version
bc 1.06.95

Personally I think the above solution is very unreadable. A fairly simple way to achieve your goal with awk could be:

Code:

awk -F: '{printf $0":";gsub(",",".");wm=$3-$2;sub("[.]",",",wm);print wm}' beurs.txt

If this doesn't work in your situation try nawk instead of awk.

Groetjes/Greetings

Eric

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LEARN ABOUT PLAN9

regexp

REGEXP(6)							   Games Manual 							 REGEXP(6)

NAME

       regexp - regular expression notation

DESCRIPTION

       A  regular  expression  specifies  a  set  of  strings of characters.  A member of this set of strings is said to be matched by the regular
       expression.  In many applications a delimiter character, commonly bounds a regular expression.  In the following specification for  regular
       expressions the word `character' means any character (rune) but newline.

       The syntax for a regular expression e0 is

	      e3:  literal | charclass | '.' | '^' | '$' | '(' e0 ')'

	      e2:  e3
		|  e2 REP

	      REP: '*' | '+' | '?'

	      e1:  e2
		|  e1 e2

	      e0:  e1
		|  e0 '|' e1

       A literal is any non-metacharacter, or a metacharacter (one of .*+?[]()|^$), or the delimiter preceded by

       A  charclass  is  a  nonempty string s bracketed [s] (or [^s]); it matches any character in (or not in) s.  A negated character class never
       matches newline.  A substring a-b, with a and b in ascending order, stands for the inclusive range of characters between a and  b.   In	s,
       the  metacharacters  an initial and the regular expression delimiter must be preceded by a other metacharacters have no special meaning and
       may appear unescaped.

       A matches any character.

       A matches the beginning of a line; matches the end of the line.

       The REP operators match zero or more (*), one or more (+), zero or one (?), instances respectively of the preceding regular expression e2.

       A concatenated regular expression, e1e2, matches a match to e1 followed by a match to e2.

       An alternative regular expression, e0|e1, matches either a match to e0 or a match to e1.

       A match to any part of a regular expression extends as far as possible without preventing a match to the remainder of the  regular  expres-
       sion.

SEE ALSO

       awk(1), ed(1), sam(1), sed(1), regexp(2)

																	 REGEXP(6)

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